By Harman Nagra
To the outside world, welding often reminds people of its importance in military applications. The modern inventions and techniques revolving around welding processes have been crucial in revolutionizing the automotive, aviation and construction industry. Despite the importance and demand among various industries for certified welders; there is a decreasing preference among engineers in pursuing a path as skilled welding personnel. For those in search of a general overview of welding processes and techniques, this is an introduction to welding of structures. A general understanding of the most commonly used welding techniques is a great place to start in realizing how metals are joined during the production of modern-day structures. Stick welding (Shielded Metal Arc Welding) is often thought as an inexpensive and common method in the industry; the welder simply uses an electrode with a constant voltage with a protective coating to penetrate or fuse the filler metal along the base metal. The coating or flux slags off as its burnt to protect against oxygen during the process. Next is Gas metal arc welding (GMAW) where the wire is fed through the welding gun using a wire spool, and a shielding gas follows in the prevention of fusion defects as the electrode does not have a flux coating. Ultimately, GMAW welding gains an advantage over SMAW due to the lack of slag that produces when flux burns so that the welder can easily see the amount of filler metal added during the process. In addition, Gas tungsten arc welding (GTAW) is another well-known method that involves holding the filler metal in a separate hand then the torch, as a gas flows through the handle and a tungsten rod is used to solely heat the base metal during the weld. Lastly, a well-utilized technique called Flux Core Arc Welding is implemented in joining metals using the same equipment as GMAW welding where the electrode is (semi or automatically) fed containing a flux, or at times in combination with a shielding gas. Knowing the mentioned methods, there are a few benefits in deciding on one over the other depending on time, space, environment and other constraints presented. Stick welding can provide the welder to finish at a fast pace if a lengthy electrode is used, especially if it has filler metal added to the coating. To put it simply, the advantage in shielded metal arc welding is the fact that it works great outdoors without the need for gas tanks, therefore simplifying the setup process. GTAW welding is regarded as a slow but high-quality technique in producing a weld, because there’s flexibility in using a stick welding machine but adding a GTAW torch and shielding gas for better quality in joining a metal. GMAW welding, on the other hand, is beneficial in terms of efficiency of welds per time unit but suffers in the limited distance the welder can travel due to the wire feeding mechanism. Moving forward, learning various weld joints used in real life applications can greatly enhance an individual’s understanding of the weld types that can be made in each of them. There are many weld types, but they all contribute to producing five basic joints (as shown in Figure 1):
- Lap Joint
- Butt Joint
- Corner Joint
- Edge Joint
Figure 1. Different Types of Weld Joints
For example, a basic lap joint allows for the following welds to be performed:
- Fillet Weld
- Bevel-Groove Weld
- J-Groove Weld
- Plug Weld
- Slot Weld
- Spot Weld
Figure 2. Different Types of Welding Performed on Lap Joint
Each of these welds have restrictions under North American Standards in designing a structure when a specific angle or stresses are present. For example, Slot and Plug welds can be used to prevent buckling, separation of lapped pieces or transmit shear. Groove and Fillet welds can be used to transmit loads assuming the welder has factored in the resistances for statically or cyclically loaded structures, and single fillet and single partial joint penetration groove welds cannot undergo bending about a longitudinal axis if there is tension at the root of the weld.
- The five basic types of joints used in welding Figure 6-1. Gas Metal Arc Welding Handbook, by William H. Minnick, November 5 2007, retrieved June 29 2018,Copyright 2007 byGoodheart-Willcox.
- Types of welds that may be made with basic lap joint Figure 6-4. Gas Metal Arc Welding Handbook, by William H. Minnick, November 5 2007, retrieved June 29 2018,Copyright 2007 byGoodheart-Willcox.
- Introduction to Welding from The Industrial Revolution to Welding Processes and Careers. (n.d.). Retrieved June 28, 2018, from http://gowelding.org/articles/introduction-welding